There are known thermoelectric conversion devices that have a plurality of N-type thermoelectric conversion elements and a plurality of P-type thermoelectric conversion elements alternately connected in series. This type of thermoelectric conversion device has been proposed as described in PTL 1.
The thermoelectric conversion device described in PTL 1 is manufactured by a method as described below. In other words, initially at a first step (a preparation step), a plurality of first and second via holes that include a thermoplastic resin and penetrate the thermoplastic resin in a thickness direction are formed. An insulating substrate that has the first via holes filled with a first conductive paste and has the second via holes filled with a second conductive paste is prepared.
Next at a second step (a laminate forming step), a front surface protecting member is disposed on a front surface of the insulating substrate, the front surface protecting member having a front surface pattern brought into contact with the first and second conductive pastes. Moreover, a rear surface protecting member is disposed on a rear surface of the insulating substrate, the rear surface protecting member having a rear surface pattern brought into contact with the first and second conductive pastes, to thereby form a laminate. At this time, at this second step, a predetermined gap is formed inside the laminate. Specifically, the predetermined gap herein referred to is a gap formed in the thermoplastic resin that configures the insulating substrate (a through hole or the like formed with a drill or the like), a gap formed in the front or rear surface pattern (a trench portion), or the like.
Next, at a third step (an integrating step), the laminate is pressed while being heated in a laminating direction by using pressing plates or the like to allow the first and second conductive pastes to configure first and second interlayer connecting members, respectively. Moreover, the first and second interlayer connecting members are electrically connected to the front and rear surface patterns. Here, as the first conductive paste, there is used one obtained by adding an organic solvent to a powder of an alloy that has a plurality of metal atoms that maintain a predetermined crystal structure, so as to form a paste. Moreover, as the second conductive paste, there is used one obtained by adding the organic solvent to a powder of a metal of a type different from that of the alloy, so as to form a paste.
Specifically, at the above-described third step, the laminate is initially heated at a temperature that allows the organic solvent to evaporate, so as to evaporate the organic solvent. Next, the laminate is pressed, while being heated at a temperature that allows the thermoplastic resin that configures the insulating substrate to fluidize (i.e., a temperature equal to or higher than a melting point of the thermoplastic resin) and is lower than a sintering temperature of each of the first and second conductive pastes. With the pressing, the first conductive paste is solid-sintered to configure the first interlayer connecting member, and the second conductive paste is solid-sintered to configure the second interlayer connecting member, while the thermoplastic resin is fluidized into the gap. In this manufacturing method, the thermoplastic resin flows (fluidizes) into the gap during pressing, and hence a pressing force applied to the thermoplastic resin (a part of the thermoplastic resin positioned around each of the first and second via holes) becomes smaller. The pressing force that would originally have been applied to this thermoplastic resin is thereby applied to the first and second conductive pastes instead. Accordingly, the pressing force applied by the pressing plates to the first and second conductive pastes becomes large, which makes it easier for each of the first and second conductive pastes are solid-sintered more reliably. Therefore, the thermoelectric conversion device manufactured by this method allows the first and second conductive pastes are solid-sintered reliably, to thereby achieve high thermoelectric conversion efficiency per unit area.
As such, at the above-described third step, the fluidization of the thermoplastic resin that configures the insulating substrate and the sintering of the first and second conductive pastes are performed simultaneously, to thereby ensure the first and second conductive pastes are solid-sintered reliably.